Symmetry features

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What we know about dark matter

There are a lot of things scientists don’t know about dark matter: Can we catch it in a detector? Can we make it in a lab? What kinds of particles is it made of? Is it made of more than one kind of particle? Is it even made of particles at all? Still, although scientists have yet to find the spooky stuff, they aren’t completely in the dark.

On background

To some degree, scientists on all of today’s particle physics experiments share a common challenge: How can they pick out the evidence they are looking for from the overwhelming abundance of all the other stuff in the universe getting in their way? Physicists refer to that stuff — the unwelcome clamor of gamma rays, cosmic rays and radiation crowding particle detectors — as background. They deal with background in their experiments in two ways: by reducing it and by rejecting it.

Physics books of 2019

The year 2019 was a banner one for Albert Einstein: It included the first image of a black hole and the 100th anniversary of the 1919 solar eclipse expeditions that validated his theory of general relativity. Learn more about both, plus topics such as quantum theory, the Hubble Space Telescope, and the science (and fiction) of “Game of Thrones” in Symmetry writer Mike Perricone’s annual list of new popular physics books.

Put it to the test beam

Test beams generally sit to the side of full-on accelerators, sipping beam and passing it to the reconfigurable spaces housing temporary experiments. Scientists bring pieces of their detectors — sensors, chips, electronics or other material — and blast them with the well-understood beam to see if things work how they expect, and if their software performs as expected. Before a detector component can head to its forever home, it has to pass the test.